Generating and updating true vertical depth indexed data and log in real time data acquisition

ABSTRACT

An invention for dynamically determining a trajectory of a drilled wellbore is provided. A method may include: receiving a piece of information including data converted from a measured physical characteristic of at least one of the wellbore or drilling the wellbore, the piece of information being relevant to determining a trajectory of the wellbore; and updating only a portion of the determined trajectory, a calculation of the portion of the determined trajectory being affected by the received data.

FIELD OF THE INVENTION

The present invention relates generally to data analysis in wellboredrilling and more specifically to dynamically determining a trajectoryof a drilled wellbore.

BACKGROUND OF THE INVENTION

During D&M or Wireline data acquisition, a large volume of time stampeddata is generated over a depth interval. The data is then gated in realtime into depth indexed data for further analysis, displaying in logs,and/or delivery to a client. Many kinds of data analyses such astemperature calculations use true vertical depth (TVD) indexed datainstead of measured depth (depth) indexed data. TVD is one of twoprimary depth measurements used by the drillers, the other beingmeasured depth. TVD refers to the vertical distance from a point in thewellbore (usually the current or final depth) to a point at the surface,usually the elevation of the rotary kelly bushing (RKB). TVDs areimportant in determining, for example, bottomhole pressures, which arecaused in part by the hydrostatic head of fluid in the wellbore. Forthis calculation, measured depth is irrelevant and TVD must be used.Typically, if no designation is used to indicate which depth measurementit refers to, the term “depth” refers to a measured depth. Note that ameasured depth, due to intentional or unintentional curves in thedrilled wellbore, is usually longer than a TVD at any given point.

It is highly desirable to transform depth indexed data into TVD indexeddata in real time. Unlike the depth index values, which depend only onthe drilling or logging direction, the TVD index values can change asthe well trajectory gets enhanced with more accepted survey stations.However, converting depth indexed data into TVD indexed data (orconverting measured depth into TVD) in real time presents a specialchallenge. In existing data acquisition systems, the real time TVD logscannot be corrected once generated since the TVD index range cannot beupdated and the depth indexed data are not re-gated over the changed TVDindex range. As a consequence, for example, the TVD logs are notcorrectly updated after a survey station is accepted.

SUMMARY OF THE INVENTION

In one embodiment of the invention, there is a method for dynamicallydetermining a trajectory of a drilled wellbore. In this embodiment, themethod comprises: receiving a piece of information including dataconverted from a measured physical characteristic of at least one of thewellbore or drilling the wellbore, the piece of information beingrelevant to determining a trajectory of the wellbore; and updating onlya portion of the determined trajectory, a calculation of the portion ofthe determined trajectory being affected by the received data.

In a second embodiment of the invention, there is a system fordynamically determining a trajectory of a drilled wellbore. In thisembodiment, the system comprises: means for receiving a piece ofinformation including data converted from a measured physicalcharacteristic of at least one of the wellbore or drilling the wellbore,the piece of information being relevant to determining a trajectory ofthe wellbore; and means for updating only a portion of the determinedtrajectory, a calculation of the portion of the determined trajectorybeing affected by the received data.

In a third embodiment of the invention, there is a computer programproduct for dynamically determining a trajectory of a drilled wellbore.In this embodiment, the computer program product comprises: computerusable program code stored in a computer useable medium, which, whenexecuted by a computer system, enables the computer system to: receive apiece of information including data converted from a measured physicalcharacteristic of at least one of the wellbore or drilling the wellbore,the piece of information being relevant to determining a trajectory ofthe wellbore; and update only a portion of the determined trajectory, acalculation of the portion of the determined trajectory being affectedby the received data.

Additional objects and advantages of the invention will become apparentto those skilled in the art upon reference to the detailed descriptiontaken in conjunction with the provided figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and not intendedto be limited by the figures of the accompanying drawings in which likereferences indicate similar elements and in which:

FIG. 1 shows a schematic block diagram of a system including a depth toTVD conversion tool according to one embodiment of this invention;

FIG. 2 shows a flow chart describing a process of converting a depthinto TVD according to one embodiment of this invention;

FIG. 3 shows examples of updating a trajectory of wellbore; and

FIG. 4 shows a computer environment which may be used to implement thedepth to TVD conversion tool.

DETAILED DESCRIPTION

Advantages and features of the present invention may be understood morereadily by reference to the following detailed description of exemplaryembodiments and the accompanying drawings. The present invention may,however, be embodied in many different forms and should not be construedas being limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete and will fully convey the concept of the invention to thoseskilled in the art, and the present invention will only be defined bythe appended claims. Like reference numerals refer to like elementsthroughout the specification. Embodiments of this invention are directedto a technique for dynamically converting measured depth to truevertical depth (TVD) and managing a cache for storing the dynamicallyupdated TVD. Although the technique is described with reference to ameasured depth of a drilled wellbore, the technique is suitable for usewith any measured depth which deviates from the respective TVD.

Referring to FIG. 1, a schematic diagram of an illustrative system 10for analyzing a wellbore 14 is shown. In FIG. 1, wellbore 14 is shown asa vertical well, but may also be other type of wells, such as a deviatedwell including a horizontal well. Wellbore 14 is shown as straight forsimplicity but it is appreciated that actual wellbores may includecurves such that a measured depth of a point in wellbore 14 is different(larger) than the respective TVD. Wellbore 14 is drilled in a reservoir16 which may include any reservoir including but not limited to oilreservoir, gas reservoir, coal reservoir, and underground waterreservoir. A measurement device(s) 20, e.g., a survey station, ispositioned along wellbore 14 to obtain information (data) related towellbore 14 or the drilling process, e.g., openhole log data.Measurement device 20 may be any solution to obtain the requiredinformation. In the description herein, “any solution” refers to anycurrently known or later developed technique to achieve a goal. Forexample, measurement device 20 may include portable rotary torquemeters, weight indicators, log devices, sink probes, observation probe,and/or the like. As drill string or tool string, which is composed ofone or more tools each tool having one or more measurement devices 20,drills further into reservoir formation 24 of reservoir 16, measurementdevices 20 may be positioned further with the progress of drillstring. Aprogress of wellbore 14 refers to the extension of wellbore 14 to thebottom thereof. As is appreciated, measurement devices 20 may bepositioned along wellbore 14 and/or may proceed into wellbore 14. FIG. 1shows that measurement devices 20(a)-(d) are positioned in earthformation 24 of reservoir 16 for clarity, which is not necessary.Measurement device 20 may be positioned within wellbore 14.

Information obtained by measurement device 20 is communicated to aprocessing center 22 via any communication solution. Processing center22 includes a depth to TVD conversion tool 24 (“TVD conversion tool24”). Conversion tool 24 includes a data receiving component 26; adisplaying component 28; a calculation component 30; a TVD conversioncomponent 32; and a cache management component 34.

Data receiving component 26 is configured to receive information fromeither outside or inside of TVD conversion tool 24 (or both). Inaddition, data receiving component 26 also includes an applicationprogramming interface (API) which functions to convert received data orinformation into a format that can be used by TVD conversion tool 24.For example, the information received from measurement devices 20 mayrepresent the physical characteristics of drilled wellbore 14 and APImay need to convert the physical characteristics into data (format) thatis recognized by TVD conversion tool 24.

Displaying component 28 functions to display the operation progress,status, and/or results of TVD conversion tool 24 as output(s) 42 to anoutside individual (human-being or machine), e.g., a user 44, which inturn may use the information to, e.g., manage the drilling of wellbore14 through instruction(s) 46.

Calculation component 30 is configured to calculate a trajectory ofdrilled wellbore 14 based on information received by data receivingcomponent 26. Calculation component 30 may also function to convert adepth of drilled wellbore 14 into a TVD based on e.g., the calculatedtrajectory of drilled wellbore 14. Calculation component 30 may applyany now know or later developed technique in the calculation thereby.

Cache management component 34 functions to manage a cache to temporarilystore a calculated trajectory of drilled wellbore 14 and/or a TVD of apoint therein. Basically, cache management component 34 may manage thecache based on a result of the calculation by calculation component 30and other related information. For example, the factor that triggers theupdating of wellbore 14 trajectory may be considered by cache managementcomponent 34 in updating the cache.

FIG. 2 shows a flow chart describing a process 100 of dynamicallydetermining a true vertical depth of a point in wellbore 14 according toembodiments of this invention. As shown in FIG. 2, the process 100begins at process block 110 where data receiving component 26 receivesinformation which is relevant to determining a trajectory of drilledwellbore 14. Specifically, data receiving component 26 receives frommeasurement devices 20 physical characteristics of wellbore 14 and mayconvert the measured physical characteristics into dataacceptable/usable by TVD conversion tool 24.

At process block 120, calculation component 30 calculates/updates aportion of the calculated trajectory of drilled wellbore 14.Specifically, only the portion of the calculated trajectory that isaffected by the newly received data will be updated. For different typesof data, the affected portion of the trajectory will be different.Consequently, calculation component 30 may only need to calculate/updatethe respective portion(s) of trajectory of drilled wellbore 14. FIG. 3shows examples of received data and updated portions of the trajectory.

In FIG. 3, blocks 200 (200 a, 200 b, 200 c shown, enclosed in a dottedblock for clarity) indicate different events (example) that cause updateof information regarding drilled wellbore 14, and blocks 210 (210 a, 210b, 210 c shown) indicate portions of the trajectory affected by the dataand thus updated by calculation component 30. At block 200 a, aTie-In-Point (TIP) for calculating the trajectory of wellbore 14 isupdated/ modified. Consequently, in the respective block 210 a, theentire trajectory will be recalculated as the Tie-In-Point affects theentire trajectory. At block 200 b, a new (first) measurement device 20,e.g., a survey station, is accepted, which obtains new informationregarding physical characteristics of drilled wellbore 14. In this case,at the respective block 210 b, the trajectory will be updated fromanother (second) measurement device 20 positioned immediately above thenewly accepted (first) measurement device 20 along a progress ofwellbore 14. That is, the updated portion of the trajectory extends fromthe (second) measurement device 20 positioned immediately above thenewly accepted (first) measurement device 20 to a deepest measurementdevice 20 positioned along the progress of wellbore 14. For example,with respect to FIG. 1, assuming measurement device 20 b is a newlyaccepted measurement device 20, calculation component 30 willupdate/calculate the trajectory of wellbore 14 from measurement device20 a that is positioned immediately above measurement device 20 b tomeasurement device 20 c which is the deepest measurement device.

As shown in FIG. 3, within block 210 b, calculation component 30 mayfurther determine whether the newly accepted measurement device ispositioned deepest along the progress of drilled wellbore 14. If thenewly accepted measurement device is the deepest one, calculationcomponent 30 may need to calculate the portion of the trajectory (fromthe immediately above measurement device 20) as the deepest measurementdevice 20 provides the updated progress of wellbore 14. If the newlyaccepted measurement device is not the deepest one, calculationcomponent 30 may need to update the already calculated trajectory (fromthe immediately above measurement device 20), as the trajectory hasalready been calculated up to the deepest measurement device 20. In thedescription herein, updating the trajectory of wellbore 14 includes thesituations of above mentioned updating and calculating operations ofcalculation component 30, unless specifically indicated otherwise.

In the description herein, the terms “deep” and “above” are defined withrespect to the progress of the drilled wellbore 14. As such, in somesituation, the “deepest” measurement device 20 may not necessarily havea higher TVD value than a measurement device portioned “above” thedeepest measurement device 20.

Returning to FIG. 3, at block 200c, an already accepted (first)measurement device 20 is rejected. Consequently, at block 210 c, thetrajectory will be updated from another (second) measurement device 20positioned immediately above the newly rejected (first) measurementdevice 20 along a progress of wellbore 14.

Returning to FIG. 2, at process block 130, TVD conversion component 32converts a depth value of a point in the drilled wellbore to a truevertical depth (TVD) based on the calculated/updated trajectory ofwellbore 14. Any now available or later developed technique may be usedin the conversion, and none limits the scope of the invention.

At process block 140, cache management component 34 manages a cachestoring the trajectory and/or the converted TVD based on the updatingthereof. Cache management component 34 only updates a portion of a cachecorresponding to the updated trajectory of wellbore 14 and/or theupdated TVD of a point of wellbore 14. For example, turning to FIG. 3 tofollow the previous example, at block 220 a, a cache will be generated/regenerated to store the calculated trajectory as the entire trajectoryis recalculated at block 210 a. At block 220 b, cache managementcomponent 34 updates/calculates a portion of the cache corresponding tothe updated/calculated portion of the trajectory of wellbore 14 resultedfrom block 210 b. Similarly at block 220 c, cache management component34 updates/calculates a portion of the cache corresponding to theupdated portion of the trajectory of wellbore 14 due to the rejection ofmeasurement device 20 b.

An alternate embodiment of the invention is as follows. A computersystem is created is created acording to FIG. 3. It is initialized withthe survey data and is responsible for all the trajectory relatedcalculations. For example, it can calculate the corresponding TVD indexvalue for any given depth index value at any time.

A client initializes the process by providing survey data to beprocessed. The survey data includes a collection of accepted surveystations. Each accepted survey station contains the measured depth,inclination from the vertical, azimuth from the north, TVD, northdisplacement, east displacement, and other related values. A TIP isentered by the field engineer. The TIP has the shallowest depth and TVDvalues (usually at the surface) and is used to tie all the otheraccepted stations together during trajectory calculations. The computersystem keeps track of all the survey related data and uses the surveydata to keep the well trajectory up to date at all times. The welltrajectory is calculated as follows:

-   1. Sort all the accepted survey stations by increasing station depth    values with the TIP at the top (shallowest depth).-   2. For any depth value between the TIP and the deepest station depth    value, use the well known minimum curvature algorithm to calculate    its other values such as TVD.    -   i. Find the enclosing shallower and deeper accepted stations.    -   ii. Interpolate the values by using the enclosing shallower and        deeper accepted stations' values.        For any depth value deeper than the deepest accepted station        depth, use straight line extrapolation to calculate the other        values.

The calculation component 30 (FIG. 2) or blocks 200 (FIG. 3) observe anychanges in the station data. If a new survey station is accepted or anaccepted survey station is rejected, block 200 b automatically re-sortsthe accepted survey stations and updates the trajectory to reflect thechanges.

The output of the computer system is a representation of the TVD indexeddata. It specifies the data type, TVD index start and stop index values,the TVD index step size (sampling rate), the cardinality which is thenumber of points, and other information. It provides TVD indexed dataaccess to the client in a transparent manner.

The client requests for TVD for a depth representation object bysupplying the depth representation as the source data. The depthrepresentation object is a representation of the depth indexed data.Just like the TVD representation, it specifies the data type, depthstart and stop index values, the depth index step size, the cardinalitywhich is the number of points, and other information.

The system responds by creating a TVD representation instance if anexisting one originated from the same depth representation is not found.The newly-created TVD representation has the same data type and stepsize as the source depth representation and the TVD representation keepsa back pointer to the depth representation for access to the depth data.The TVD representation object also keeps a pointer to a cache in block220 for any depth and TVD index conversions.

The TVD representation object then initializes itself. It first fetchesthe depth index range from its source depth representation object. Itthen gets the TVD index range from block 220 corresponding to the depthindex range. Finally, it calculates the number of TVD data points withthe formula: Number of TVD data points=absolute value (TVD stopindex−TVD start index)/TVD step size. The TVD representation is thenprovided to the client.

The client can then use the returned TVD representation object to fetchthe TVD indexed data. The client can first ask the TVD representationobject for its cardinality which represents the number of TVD points ascalculated above. Using the cardinality value, it can then loop throughto get some or all of the TVD index and data values.

The TVD index values are directly calculated and returned with theformula: TVD Index=TVD start index+i*TVD step size where 0<=i<TVDcardinality is the zero-based TVD ordinal number.

The TVD data value for a given TVD index value is found by block 220 andthen getting its corresponding depth data value from the source depthrepresentation object.

As the real time drilling or logging job goes on, the clientperiodically calls the TVD representation's refresh method to update theTVD index values and ranges dynamically. The TVD representation forwardsits refresh call to the block 220 refresh method, which performs theactual TVD index range updates.

Block 220 performs all the depth index to TVD index and TVD index todepth index conversions and keeps track of them in its internal cache.When an open survey station is accepted or an accepted survey station isrejected, the cache is invalidated and rebuilt as needed. As the depthindex range changes during logging or drilling, the internal cache isupdated to reflect the new depth index range.

The foregoing flow chart shows some of the processing functionsassociated with preparing an electronic document of a log containingcontinuous information for both continuous and page-by-page printingaccording to one embodiment of this invention. In this regard, eachblock represents a process act associated with performing thesefunctions. It should also be noted that in some alternativeimplementations, the acts noted in the blocks may occur out of the ordernoted in the figure or, for example, may in fact be executedsubstantially concurrently or in the reverse order, depending upon theact involved. Also, one of ordinary skill in the art will recognize thatadditional blocks that describe the processing functions may be added.

FIG. 4 depicts a block diagram of a general-purpose computer system 300that can be used to implement data correction tool 300. Data correctiontool 300 may be coded or deployed as a set of instructions on removableor hard media for use by the general-purpose computer 300. The computersystem 300 has at least one microprocessor or central processing unit(CPU) 305. The CPU 305 is interconnected via a system bus 320 to machinereadable media 375, which includes, for example, a random access memory(RAM) 310, a read-only memory (ROM) 315, a removable and/or programstorage device 355, and a mass data and/or program storage device 350.An input/output (I/O) adapter 330 connects mass storage device 350 andremovable storage device 355 to system bus 320. A user interface 335connects a keyboard 365 and a mouse 960 to the system bus 320, a portadapter 325 connects a data port 345 to the system bus 320, and adisplay adapter 340 connects a display device 370 to the system bus 320.The ROM 315 contains the basic operating system for computer system 300.Examples of removable data and/or program storage device 355 includemagnetic media such as floppy drives, tape drives, portable flashdrives, zip drives, and optical media such as CD ROM or DVD drives.Examples of mass data and/or program storage device 350 include harddisk drives and non-volatile memory such as flash memory. In addition tothe keyboard 365 and mouse 960, other user input devices such astrackballs, writing tablets, pressure pads, microphones, light pens andposition-sensing screen displays may be connected to user interface 335.Examples of the display device 370 include cathode-ray tubes (CRT) andliquid crystal displays (LCD).

A machine readable computer program may be created by one of skill inthe art and stored in computer system 300 or a data and/or any one ormore of machine readable medium 375 to simplify the practicing of thisdisclosure. In operation, information for the computer program createdto run the present disclosure is loaded on the appropriate removabledata and/or program storage device 355, fed through data port 345, orentered using keyboard 365. A user controls the program by manipulatingfunctions performed by the computer program and providing other datainputs via any of the above mentioned data input means. The displaydevice 370 provides a way for the user to accurately control thecomputer program and perform the desired tasks described herein.

Computer readable media can be any available media that can be accessedby a computer. By way of example, and not limitation, computer readablemedia may comprise “computer storage media” and “communications media.”

“Computer storage media” include volatile and non-volatile, removableand non-removable media implemented in any method or technology forstorage of information such as computer readable instructions, datastructures, program modules, or other data. Computer storage mediaincludes, but is not limited to, RAM, ROM, EEPROM, flash memory or othermemory technology, CD-ROM, digital versatile disks (DVD) or otheroptical storage, magnetic cassettes, magnetic tape, magnetic diskstorage or other magnetic storage devices, or any other medium which canbe used to store the desired information and which can be accessed by acomputer.

“Communication media” typically embodies computer readable instructions,data structures, program modules, or other data in a modulated datasignal, such as carrier wave or other transport mechanism. Communicationmedia also includes any information delivery media.

The term “modulated data signal” means a signal that has one or more ofits characteristics set or changed in such a manner as to encodeinformation in the signal. By way of example, and not limitation,communication media includes wired media such as a wired network ordirect-wired connection, and wireless media such as acoustic, RF,infrared, and other wireless media. Combinations of any of the above arealso included within the scope of computer readable media.

While shown and described herein as a method and system for performing adata correction on a hierarchical integrated circuit layout, it isunderstood that the disclosure further provides various alternativeembodiments. For example, in an embodiment, the disclosure provides aprogram product stored on a computer-readable medium, which whenexecuted, enables a computer infrastructure to perform a data correctionon a hierarchical integrated circuit layout. To this extent, thecomputer-readable medium includes program code, such as data correctiontool 300 (FIG. 4), which implements the process described herein. It isunderstood that the term “computer-readable medium” comprises one ormore of any type of physical embodiment of the program code.

It should be appreciated that the teachings of the present disclosurecould be offered as a business method on a subscription or fee basis.For example, a computer system comprising data correction tool 300 (FIG.4) could be created, maintained and/or deployed by a service providerthat offers the functions described herein for customers. That is, aservice provider could offer to provide a service to perform a datacorrection on a hierarchical IC layout as described above.

As used herein, it is understood that the terms “program code” and“computer program code” are synonymous and mean any expression, in anylanguage, code or notation, of a set of instructions that cause acomputing device having an information processing capability to performa particular function either directly or after any combination of thefollowing: (a) conversion to another language, code or notation; (b)reproduction in a different material form; and/or (c) decompression. Tothis extent, program code can be embodied as one or more types ofprogram products, such as an application/software program, componentsoftware/a library of functions, an operating system, a basic I/Osystem/driver for a particular computing and/or I/O device, and thelike. Further, it is understood that the terms “component” and “system”are synonymous as used herein and represent any combination of hardwareand/or software capable of performing some function(s).

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Although specific embodiments have been illustrated and describedherein, those of ordinary skill in the art appreciate that anyarrangement which is calculated to achieve the same purpose may besubstituted for the specific embodiments shown and that the disclosurehas other applications in other environments. This application isintended to cover any adaptations or variations of the presentdisclosure. The following claims are in no way intended to limit thescope of the disclosure to the specific embodiments described herein.

It is apparent that there has been provided by this invention anapproach for performing data correction operation on an IC layoutaccommodating compensation for CD variations. While the invention hasbeen particularly shown and described in conjunction with a preferredembodiment thereof, it will be appreciated that variations andmodifications will occur to those skilled in the art. Therefore, it isto be understood that the appended claims are intended to cover all suchmodifications and changes as fall within the true spirit of theinvention.

1. A method for dynamically determining a trajectory of a drilledwellbore, comprising: receiving a piece of information including dataconverted from a measured physical characteristic of at least one of awellbore or drilling the wellbore, the piece of information beingrelevant to determining a trajectory of the wellbore; and updating onlya portion of the piece of information relevant to the determinedtrajectory, a calculation of the portion being affected by the receiveddata.
 2. The method according to claim 1, wherein the measured physicalcharacteristic is provided by a first measurement device.
 3. The methodaccording to claim 2, wherein the portion is calculated from a secondmeasurement device positioned above the first measurement device along aprogress of the wellbore to a deepest measurement device positionedalong the progress of the wellbore.
 4. The method according to claim 1,wherein the piece of information indicates that a previously acceptedmeasurement device is rejected.
 5. The method according to claim 4,wherein the portion is calculated from a measurement device positionedabove the rejected previously accepted measurement device along aprogress of the wellbore to a deepest measurement station positionedalong the progress of the wellbore.
 6. The method according to claim 1,further comprising updating a provided cache storing the determinedtrajectory with only the updated portion of the trajectory.
 7. Themethod according to claim 1, wherein where the piece of informationindicates a modification of a tie-in point for the determination of thetrajectory, the updating includes calculating the entire trajectory. 8.The method according to claim 7, further comprising generating a cachefor the calculated entire trajectory.
 9. The method according to claim1, further comprising calculating and updating a true vertical depth ofa point of the wellbore based on the determined trajectory.
 10. A systemfor dynamically determining a trajectory of a drilled wellbore,comprising: means for receiving a piece of information including dataconverted from a measured physical characteristic of at least one of thewellbore or drilling the wellbore, the piece of information beingrelevant to determining a trajectory of the wellbore; and means forupdating only a portion of the information relevant to determining atrajectory, a calculation of the portion of being affected by thereceived data.
 11. The system according to claim 10, wherein thephysical characteristic is provided by a first measurement device. 12.The system according to claim 11, wherein the updating means calculatesthe portion from a second measurement device positioned above the firstmeasurement device along a progress of the wellbore to a deepestmeasurement device positioned along the progress of the wellbore. 13.The system according to claim 10, wherein the piece of informationindicates that a previously accepted measurement device is rejected. 14.The system according to claim 13, wherein the updating means calculatesthe portion from a measurement device positioned above the rejectedpreviously accepted measurement device along a progress of the wellboreto a deepest measurement station positioned along the progress of thewellbore.
 15. The system according to claim 10, further comprising meansfor updating a provided cache storing the determined trajectory withonly the updated portion.
 16. The system according to claim 10, whereinwhere the piece of information indicates a modification of a tie-inpoint for the determination of the trajectory, the updating meanscalculates the entire trajectory.
 17. The system according to claim 16,further comprising means for generating a cache for the calculatedentire trajectory.
 18. The system according to claim 10, furthercomprising means for calculating and updating a true vertical depth of apoint of the wellbore based on the determined trajectory.
 19. A computerprogram product for dynamically determining a trajectory of a drilledwellbore, comprising: computer usable program code stored in a computeruseable medium, which, when executed by a computer system, enables thecomputer system to: receive a piece of information including dataconverted from a measured physical characteristic of at least one of thewellbore or drilling the wellbore, the piece of information beingrelevant to determining a trajectory of the wellbore; and update only aportion of the information relevant to the determined trajectory, acalculation of the portion being affected by the received data.
 20. Theprogram product according to claim 19, wherein the data indicating achange of the physical characteristic related to a first measurementdevice, and the portion is calculated from a second measurement devicepositioned immediately above the first measurement device along aprogress of the wellbore to a deepest measurement device positionedalong the progress of the wellbore.
 21. A method for converting depthindexed data into true vertical depth indexed data in a wellborecomprising: providing depth indexed data from a plurality of surveystations along the wellbore; receiving a piece of information includingdata converted from a measured physical characteristic of each of theplurality of survey stations, the piece of information being relevant todetermining a trajectory of the wellbore; updating only a portion of theinformation relevant to the determined trajectory from each of theplurality of survey stations, a calculation of the portion of beingaffected by the received data; calculating and updating a true verticaldepth for each of the survey stations of the wellbore based on theupdated portion; and providing true vertical depth indexed data for theplurality of survey stations along the wellbore.